The State Department still has some explaining to do after a closed briefing Thursday with Senate Foreign Relations Committee members over allegations that a report vital to several administration initiatives was watered down for political purposes.

Committee members have cried politics since July when the annual Trafficking in Persons report was released. After Thursday's briefing, senators called for more transparency in the process that saw Malaysia and Cuba upgraded from the lowest ranking in terms of human-trafficking conditions. “My concerns were not alleviated in any way,” Chairman Bob Corker, R-Tenn., said. “I don’t think there is anybody who was there that didn’t feel even more firmly that politics played a major role in determining some of the upgrades in the TIP report.”

Corker said he requested documentation explaining the decision-making process. “I also think you’re going to see a push towards legislation so that there’s transparency when a country is getting ready to be upgraded … into what is going into that consideration and allow us to weigh in accordingly,” Corker said.

Ranking Democrat Benjamin L. Cardin of Maryland said he hadn’t requested any documentation on internal deliberations, adding that the administration should be allowed to conduct some discussions in private. But, he also said there needed to be more transparency, which could be strengthened through existing law.

“We do need to know whether there are outside considerations that need transparency before decisions were made on countries' rankings,” Cardin said. “So that, I think, is important for us to get access to.”

Cardin said he was still not convinced Malaysia deserved its improved ranking.

The TIP report is used to publicly shame the worst human-rights violators and an upgraded status allows the Trans-Pacific Partnership to continue along a fast-track path with Malaysia included, and helps justify recently renewed relations with Cuba.

Prior to the release of the TIP report, fast-track trade legislation was signed into law with a provision, pushed by Sen. Robert Menendez, D-N.J., barring expedited consideration of a country with a Tier 3 ranking.

Menendez, who served as ranking member on the panel before he was indicted , was one of the most outspoken critics of the report and said the explanations Thursday didn’t differ from prior explanations and that he “may have a few other ideas about what comes next.”

Deputy Secretary of State Antony Blinken, who addressed the committee on this year's TIP report process, declined to speak to reporters.

But at a hearing just before the August recess, State Department Under Secretary Sarah Sewall said in her opening statement: “Tier rankings do not assess the severity of human trafficking in a given country, but rather that government’s efforts in addressing human trafficking problems over the current reporting period compared to its own efforts in the prior year."

Senators want to protect the integrity of the report, which tracks improvements in human trafficking throughout the world and sets benchmarks for success.

“All we want to do is to make sure that program is accurate, it maintains its efficacy and can be used objectively in working with these countries to improve their record,” said Sen. David Perdue, R-Ga. “Most countries out there are really trying to improve their record, but we just want to make sure that the starting point is always accurate every year.”

Fueling detractors' disdain is an August Reuters article that found the TIP offices’ recommendations were overruled 14 out of 17 times by diplomatic bureaus and that the TIP office recommended that neither Malaysia or Cuba be upgraded.

The State Department has been reluctant to provide details about how the decisions over the upgraded rankings were reached, but Sen. Christopher S. Murphy, D-Conn., said that was “understandable” and that “clearly, there was no political influence involved in the decisions that they made.”

The State Department’s Office to Combat and Monitor Trafficking in Persons, which produces the TIP report, has been without a principal since last November, when former Ambassador-at-Large Luis C. de Baca departed to take a job at the Justice Department. The lack of a leader has raised concerns among some, including Corker, that the office was less-equipped this year to push back against suspected intra-department efforts to water down the TIP report’s findings.

A successor to de Baca was nominated in July. Corker has scheduled a confirmation hearing next week for the nominee, Susan Coppedge, a longtime assistant United States attorney for the northern district of Georgia.

In recent years, U.S. efforts to combat global modern day slavery have been largely congressionally led. The annual TIP report is legally required under the 2000 Trafficking Victims Protection Act. The law, which has been repeatedly reauthorized and amended, spells out minimum standards countries should take to combat human trafficking and how the State Department is to assess whether those standards are being met. The law also established the department’s Office to Combat and Monitor Trafficking in Persons.

Earlier this year, the Foreign Relations Committee advanced a bill sponsored by Corker that would create a nonprofit grant-making organization focused on combating human trafficking and would authorize approximately $251 million toward the effort.